Machine-switching telephone-exchange system



Dec. 25 1923.

C. L. GOODRUM MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Dec. 31 1919 In vemor:

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oHAnLEs L. GOODRUM, E N W YORK, N. Y.. ASSIGNOR 'ro wEsrEaN ELECTRIC COM- PANY, INCORPORATED, or NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTEM.

Application filed December 31, 1919. Serial No. 348,578.

T 0 all whom it may concern. I

Be it known that I, CHARLES L.- Goon- RUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Machine-Switching Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone exchange systems, and more particularly to such systems wherein toll connections are completed by an operator. Its object is to provide an improved circuit arrangement for checking the number given the operator by the calling subscriber, such toll operators positions being selected over an automatic switch or switches. In such event she ordinarily has no means of ascertaining the number of the calling line except from the subscriber.

In accordance with this invention, the operator is provided with a special set of automatic switches by means of which she may connect with multiples of the calling line and impress thereon a tone which is transmitted back over the connection built up for the subscriber and into the headset of such operator, this tone being impressed upon the talking conductors of the special switches and of the switches in the Connection built up for the subscriber in multiple, so that while the operator can hear the tone, the calling subscriber cannot. It is desirable to avoid impressing unnecessary tones on subscribers lines to pre vent confusion, since it is becoming the practice to notify subscribers by means of different tones of the condition or progress of calls as, for example, busy and ringing tones.

Referring to the drawing, A designates the calling substation which, by means of a first selector B, is associated with a trunk C which terminates in a jack before the toll operator, who, in response to the lighting of the calling lamp associated therewith, extends the call by means of a plug to a trunk D terminating in a plug, which, after the operator has secured the desired number, she inserts into a jack T which terminates in a first selector. This selector and succeeding automatic switches are set by the operator to build up a connection to a desired line. The circuits and apparatus are not shown in detail since they may be identical with those shown in-Fig. 1, parts 1 and 2 of Patent ai -1,251,350, December 25', 1917, to Gerald Deakin. The operator then by means of her key DK connects her dial CD to a first selector L and sets the same'to pick out a connector M, which she then sets on the line given her by the calling subscriber. Upon completing the connection she depresses hen listening key LK, and if the subscriber gave the correct number she will hear a tone in her head-set, from the tone source TT over the talking conductors in multiple. If, however, the calling subscriber, gave some other number, wipers 112 and 113 would have been connected to multiples of some line which is not connected back through cord circuit D, so that when the operator connected the tone 118 to the checking circuit, the signal would not be received and she would know that something is wrong. After the checking operation, the operator by actuatin key DK' causes the special switches L, lid to be restored.

More specifically, when the toll operator answers the call to ascertain the wants of the calling subscriber, she also requests the number of the calling substation, which in the case of toll service is used to make the toll charge, as is Well understood. In the drawings is indicated by the diagrammatic circuits A, B, C, D, T a connectiOnestablished from calling substation A to trunk T. Trunk T terminates in a selector as shown in figure, part 2, of the patent referred to, which is then set to pick out a connector to connect with the called line as fully shown and described in said patent.

Having ascertained the number of the calling telephone line A, which we will assume is No. 345, the operator throws a calling device key DK to connect a calling device CD in circuit with a selector switch L, this connection resulting in the energizationof impulse relay 1R over the metallic circuit including the contacts of said device CD'fland responsive to energization of IE its alternate contact 15 is closed, causing the energization of release allowin magnet Pv a retract its armature anc step the side-switch arms into their second position. A. vibratory circuit for rotary magnet RM is thereby established, causing it to operate to step wipers 101 to 105 inclusive into engagement with the first set of contacts 106 to 110 inclusive in the selected level, and due to a mechanical con nection thefirst operation of RM moves the armature of'magnet PV into its attracted position, whereby if the first set of contacts engaged lead to a busy second selector M, relay PV ismaintained energized and the magnet RM continues to step the wipers until an idle set of contacts is reached, 'whereby the maintaining circuit for PV is interrupted, causing it to. deenergize and move the side-switch arms into their third position thus preventing any fur-- ther operations of RM and extending the metallic circuit including calling device CD over the heavily marked conductors and through the impulse relay IE to battery, causing its energization.

Closing of alternate contact 111 of relay 1R connects ground to themultiple contacts 106 preventing any other switch L from con necting to switch M, this connection also being adapted to maintain relay BB energized. Also upon closing of alternate contact 111, release relay ER is energized.

The operator now actuates calling device CD to effect four operations of relay 1R whereby four impulses are transmitted through SR, VM, and vertical magnetVM is operated four times to cause four vertical steps of wipers 112, 113, while secondary relay SR due to the closing of its alternate contact 114, causes private magnet RV to step side-switch arm 115 into its middle position after the said four operations. The operator again actuates calling device CD this time effecting five operations of relay IR resulting in five operations of rotary magnet RM and stepping wipers 112, 113 into engagement with the fifth set of contacts 4, 5, which are the terminals of substation No. 345. During this rotary operation of the wipers, they are disconnected at normal contacts 115, 116 respectively so that no existing connections will be interfered with. After the last said five operations, private magnet RV steps the side switch arm into its third position due to the circuit through alternate contact 114. 7

Thus, it will be seen that if the calling subscriber has given the correct number, a

.circuit will be established from key DK' over the heavily marked conductors to the terminals of the calling line and then over circuits B, C, D, to operators circuit 0, so that upon the operator throwing her key DK to connect test-tone device TT in cirwit, a signal will .be transmitted over the circuit including switches L, M, B and circuits B, 0,1), to the. operators telephone set 0, which is adapted to be connected to the circuit D by a listening key LK whereby she receives the signal and is thus informed that the subscriber has given the correct parallel, talking trunks O, D in parallel,

through the contacts of listening key LK to the opposite ends of the primary winding is heard by the operator by means of her receiver R, the key shown in the head set circuit 0 being thrown to its alternate position. In its normal position this key disconnects said secondary winding S from said receiver R and connects the receiver to the alternate contacts of the listening key LK sothat the operator may communicate with subscribers by a circuit including the trunk conductors in series. An examination of the tone circuit traced will show that the tone current can only pass from groundthrough the secondary of induction coil 118 of apparatus TT, over the conductors of trunks L, M and multiple wiring between switches M and B in parallel, through the trunk conductors B, C and D in parallel, key LK, the primary winding P of the induction coil in the head set, which primary winding induces current in the secondary winding S,

to which the operatorsreceiver It is con nected when the key in the head set is thrown to its alternate position, as described. Since thcre is no ground at substation A, this tone current cannot flow out over the conductors leading to substation A but must flow over the path just traced, to ground at the middle point of primary winding P of the induction coil in the operators head set. Therefore, since this current cannot find a path to ground at the substation A, tone will not be heard in the nuance receiver at said substation and the calling subscriber will not be awareof the checking operation being performed by the operator to see whether the subscriber has given the right number.

It will be apparent that it the calling subscriber gave some other number than his own, that wipers 112, 113 would have been connected to terminals 4, 5 of some line which is not connected back through cord circuit 1), so that when the operator connected the test tone TT to the checking circuit the signal would not be received and she would know that something was wrong.

After the checking operation has been per formed, by restoring key DK to its normal position, the circuit for relay IE is interrupted causing its restoration, and due to the interruption of its alternate contact 111 release relays RR and BB are restored, the restoration of relay BB closing its normal contact 16 whereby a circuit for release magnet REM is established from ground through normal contacts 15, 16, the winding of REM through oit-normal switch 0N to battery, causing the energization of the release magnet, whereby switch L is restored in a well known manner.

Upon restoration of RR*, its normal contact 111 is closed whereby an energizing circuit for release magnet RENE is established through oft-normal switch 0N causing restoration of switch Min a well-known manner, whereby switches L and M are now available for use in performing other cheeking operations.

lVhat is claimed is:

1. A telephone system comprising telephone lines, operator controlled link circuits, automatic switches for interchangeably connecting said lines and link circuits responsive to calls over said lines, connection terminals for said lines, operator controlled automatic switches tor connecting to said terminals of a calling line, and means including a circuit comprising-the talking conductors in parallel for transmitting a characteristic signal to a connected operators link circuit.

2. A telephone system comprising telephone lines, operator controlled link circuits, an automatic switch connected with one of said link circuits responsive to a call over said lines, connection terminals for said lines, operator controlled automatic switches for connecting to said terminals of a calling line, and means for transmitting a characteristic signal over the established talking circuit in parallel including said antomatic switches in the operators link cirsuit.

3. A telephone system including a telephone line, operator controlled link circuits, an automatic switch for connecting said line with one of said link circuits responsive to a call over said line, means for establishing a circuit over said line, a link circuit whereby the operator may learn the number of the calling telephone line from the calling subscriber, and means controlled by the operator including a circuit over the talking conductors in parallel for ascertaining whether the telephone number given by a calling subscriber is the number of the calling line. v

4. A telephone system including telephone lines, operator controlled link circuits, automatic switches for interchangeably con necting said lines and link circuits responsive to calls over said lines, means cont-rolled by theoperator for establishing a conversational circuit over such a connection whereby she may learn the number of the calling telephone line from the calling subscriber, and means including a circuit over said talking conductors in parallel controlled by the operator for ascertaining whether the telephone number given by the calling subscriber is the number of the calling line.

5. A telephone system including a telephone line, operator controlled link circuits, an automatic switch for connecting said line to one of said link circuits responsive to a call over said line, means for establishing a conversational circuit between said calling line and link circuit whereby the operator may learn the number of the calling line from the calling subscriber, operator controlled automatic switches for connectthe number given by the calling subscriber, and a circuit including the talkin conductors in parallel for determining whether the telephone line connected with is the call ing telephone line.

6. A telephone system including a telephone line, operator controlled link cir cuits, an automatic switch for connecting said line with an idle one of said link circuits responsive to a call over said line,

means controlled by the operator for connecting to the line corresponding to the number given by the calling subscriber, and means including a circuit over said talking conductors in parallel for determining whether the telephone line connected with is the calling telephone line.

'7. A telephone system comprising calling and called telephone lines, and means controlled by an operator including operator controlled automatic'switches and a circuit in parallel over the talking conductors of said switches for checking thenumber of the calling line.

8. A telephone system comprising telephone lines, operator controlled link circuits, switches for interchangeably connecting said lines and link circuits responsive to calls over said lines, connection terminals for said lines, and operator controlled elecing to the telephone line corresponding to tromagnetic switches for operatively connecting to the terminals of a line that is calling and is connected to one 01 said link circuits, and means including a circuit over the talklng conductors in parallel for giving a characteristic signal to the operator.

9. A telephone system comprising telephone lines, a central office operators switchboard, operator controlled link circuits thereat, switches responsive to calls over said lines for interchangeably connecting said lines and link circuits, called line connection terminals of said lines, and electromagnetic switches controlled by an operator at the central otlice switchboard for connecting to the called line terminals of a line-that is calling and is operatively connected in telephonic circuit with one of said fli'nk circuits, and a circuit including the switches through the last terminals and through the first said switches to the operators link circuit.

11. A telephone system including a telephone line, a central oiiice operators switch- I heard, an operators link circuit, means for connecting said telephone line to said link circuit, an operator controlled electromagnetic switch for connecting to said link circuit through terminals of said line, and means including the talking conductors in parallel for transmitting a tone over said switch to the operators set associated with said link circuit.

12. A telephone system including a telephone line, a central office switchboard, a linkcircuit at said switchboard, electromagnetically controlled means for connecting said line to said link circuit, a tone source, an operator controlled electromagnetic means for connecting to said line, a tone from said source in parallel over the talking conductors of said line circuit.

13. A machine switching telephone 6X- change system including a calling line, a link circuit, automatic switches adapted upon the initiation of a call to connect said line with an idle link circuit, means controlled by the operator for extending the calling line to the called line, a special circuit controlled by the operator and having associated therewith a tone source, means for connecting said source in parallel to the conductors of; said special circuit and thereby to multiples of the calling line and to thelink circuit connected to the calling line and over which'the connection is built up, an operators telephone, and a key for connecting the sameto 1 said link circuit. 7

- 14. In a telephone system, a calling line, link circuits, means for automatically connecting a calling line to an idle link circuit, means for extending said link circuit to the called line, a special circuit,'a tone source including a primary and secondary winding toll trunks, trunk circuits terminating in an operators position, means under the control of the calling subscriber for causing said selector to seize one of said toll trunks, means controlled by the operator for extending said trunk into connection with a called line, a checking circuit including automatic switches and a tone source including a primary and secondary winding the secondary winding of which has its middle point connected to ground, means controlled by the operator for building up a connection over said switches to the calling line and a key for connecting the opposite ends of said secondary winding to the talking conductors of the connection thus built up whereby said tone is transmitted to the talking conductors ofthe trunk circuit-in parallel, an operators circuit including an induction coil having the middle point of its primary winding connected to ground, and a key for connecting the opposite ends of said winding to said talking conductors.

In witness whereof, I hereunto subscribe my name this 30th day of December, A. D.

CHARLES GOODRUM. 

